The present invention generally relates to a heat exchanger for an internal combustion engine. More specifically, the invention relates to an integrated heat exchanger and expansion tank for cooling a marine engine.
Liquid-cooled internal-combustion engines for marine applications usually utilize a heat exchanger wherein heat is transferred from liquid engine coolant to seawater. Facilitating this thermal exchange is a heat exchanger core comprised of one or more seawater tubes through which seawater is continually passed. The engine coolant is directed to flow externally over the core, so that heat from the coolant is absorbed into the cooler seawater. Coolant is then recirculated through a coolant circuit to cool the engine block, and in certain applications, to cool a turbocharger and/or exhaust manifold.
Vapor and air bubbles sometimes emerge in the liquid coolant of a cooling system. The vapor tends to rise and collect at certain locations, if permitted. The presence of vapor and air in the cooling circuit undesirably reduces the thermal exchange capacity at the vacinity of trapped vapor. Therefore, it is desirable to de-aerate the liquid coolant in the heat exchanger so that any vapor and air bubbles are collected and removed from the cooling circuit. Additionally, it is desirable to "vent" vapor pockets from remote locations of the cooling circuit.
A conventional cooling system usually includes an expansion chamber containing a volume of air in communication with the cooling circuit. This permits volume variations in the liquid coolant without overpressurizing or damaging the system. Ideally, vapor and air from the cooling circuit are collected at the expansion chamber. An expansion chamber may additionally function as a make-up reservoir, containing extra coolant to compensate for coolant losses in the system.
Conventional cooling systems typically include separate, discrete heat exchanger and expansion tank components. These discrete components must be connected in fluid communication with each other by hoses, hose clamps and tubing. Moreover, a separate coolant collection reservoir tank is sometimes provided in conventional systems as a third additional component which must likewise be connected with hoses and mounted to the engine. Unfortunately, these conventional arrangements are susceptible to failure of the hoses or leakage at the clamped hose connections. Furthermore, the separate heat exchanger, expansion tank, and collection reservoir tank components are known to inconveniently obstruct other engine parts due to their bulky nature, and additionally give the engine an aesthetically unpleasing bulky or cluttered appearance.
Engine rooms or engine bays in boats are usually confined spaces. Accordingly, a compact engine design is desirable in order to maximize space surrounding the engine in an existing engine compartment, or in order to minimize engine compartment size.
Over time and use, a marine heat exchanger core accumulates debris from the seawater, requiring cleaning to optimize heat conduction and water flow. Cleaning of the core tubes is typically performed by a process known as "rodding" in which a rod-like tool is manually inserted through the tubes, pushing any debris through the tubes. Unfortunately, conventional marine heat exchangers are difficult to clean because of inadequate access. In conventional heat exchangers, the core must be removed from the heat exchanger housing in order to permit "rodding" of the seawater tubes.
More specifically, a conventional core is provided as a unit with a header cap mounted at one end for porting seawater flow to and from the core interior. This core is inserted through a single opening into the heat exchanger housing, the core being mounted in position by securing the header cap over the housing opening. Access to the core interior for cleaning requires that the header cap first be disassembled from the housing, withdrawing the core from the housing with the header cap attached, and removing the header cap from the core. This is disadvantageous, because removal of the core exposes the engine coolant side of the cooling system, draining the engine coolant from the heat exchanger and risking contamination of the housing interior with debris. Moreover, in many instances, withdrawal of the core from the heat exchanger housing may be impossible in the field due to obstruction by an engine component or engine room wall. Therefore, a heat exchanger design is needed which permits "rodding" of the core without removing the core from the housing.